Maltopentaose-forming .alpha.-amylase derived from microorganisms belonging to the genus Pseudomonas can be used to enzymatically produce maltopentaose from starch etc.
However, said enzyme has an additional activity of decomposing the resulting maltopentaose into maltotriose and maltose. Accordingly, decomposition of the formed maltopentaose does also proceed with time to reduce the yield of maltopentaose and to simultaneously generate maltotriose and maltose as by-products. Therefore, it was difficult to produce maltopentaose efficiently by use of said enzyme.
An object of the present invention is to develop an improved enzyme, which has an enhansed practical usability, by modification to the gene of said enzyme to reduce the activity of decomposing maltopentaose.